iridium (Ir)

Iridium (Ir) is a very hard and brittle, exceptionally corrosion-resistant,
silvery-white metallic element. Iridium
is a transition element and a
member of the platinum group. It
occurs in platinum ore and is used principally
to harden platinum and in high-temperature materials, surgical and scientific
instruments, electrical contacts, pen tips, and and wear-resistant bearings.
It is also used to encapsulate radioactive fuels on spacecraft. Discovered
by Smithson Tennant in London in 1803, its name comes from the Latin iris (stem irid-) for "rainbow," from the variety of colors in gives
in solution. Its most common isotope is 193Ir (62.6%).